Coccidiosis is a species specific parasite,and every animal including man carries a form of it,although not at levels that interface with activity or digestion. In pigeon ,coccidiosis is an intestinal disease caused by a single-celled protozoan parasite,usually Eimeria labbeana or E. columbarum. The life cycle of the parasite is quite complicated,but basically,when it infects in large numbers, it destroys the cell in the intestinal walls,each time releasing more protozoa into the intestine, infecting the semi digested food, and attacking new cells,Seriously infected pigeons rapidly lose weight and their droppings become watery